Probably offtopic, but would you mind expanding a bit on the mentor requirement a bit? Being in a similar position, I'm a little embarrassed that's not something I've considered so far and that made me a little bit anxious.
But basically everything we've found in rigorous study suggests that to master something you need a mentor/coach. It's not that you can't' figure the stuff out on your own. It's that you will save tremendous amounts of time by not doing so.
So one of the big weaknesses of going to work for as startup, especially as a newish dev, is that the mentorship opportunities are frequently lacking (startups have a hard time paying what mentors are worth). But this just means that you have to account for that in other ways:
- make sure your next job is geared around the mentorship opportunities
- go out of your way to develop mentorship relationships outside of work.
There are lots of very good benefits to working at startups. Just be aware of the trade off and make sure you are accounting for it in your career plan. Careers are long, no reason you have to optimize for each thing at each job.